The present invention relates to subterranean treatments, and more particularly, to aqueous subterranean treatment fluids that comprise friction reducing copolymers and associated methods.
Aqueous treatment fluids may be used in a variety of subterranean treatments. Such treatments include, but are not limited to, drilling operations, stimulation operations, and completion operations. As used herein, the term “treatment,” or “treating,” refers to any subterranean operation that uses a fluid in conjunction with a desired function and/or for a desired purpose. The term “treatment,” or “treating,” does not imply any particular action by the fluid.
An example of a stimulation operation utilizing an aqueous treatment fluid is hydraulic fracturing. In some instances, a fracturing treatment involves pumping a proppant-free, aqueous treatment fluid (known as a pad fluid) into a subterranean formation faster than the fluid can escape into the formation so that the pressure in the formation rises and the formation breaks, creating or enhancing one or more fractures. Enhancing a fracture includes enlarging a pre-existing fracture in the formation. Once the fracture is formed or enhanced, proppant particulates are generally placed into the fracture to form a proppant pack that may prevent the fracture from closing when the hydraulic pressure is released, forming conductive channels through which fluids may flow to the well bore.
During the pumping of the aqueous treatment fluid into the well bore, a considerable amount of energy may be lost due to friction between the aqueous treatment fluid in turbulent flow and the formation and/or tubular goods (e.g., pipes, coiled tubing, etc.) disposed within the well bore. As a result of these energy losses, additional horsepower may be necessary to achieve the desired treatment. To reduce these energy losses, friction reducing polymers have heretofore been included in aqueous treatment fluids. The friction reducing polymer should reduce the frictional losses due to friction between the aqueous treatment fluid in turbulent flow and the tubular goods and/or the formation.
In some instances, the friction reducing polymers that have been used previously are suspended in oil-external emulsions, wherein upon addition to the aqueous treatment fluid, the emulsion should invert releasing the friction reducing polymer into the fluid. One such friction reducing polymer is a copolymer of acrylic acid (in an amount of 30% by weight) and acrylamide (in an amount of 70% by weight). However, it is believed that the ionic nature of certain of these friction reducing polymers (such as the aforementioned copolymer) may cause the friction reducing polymers to function as flocculants. This may be undesirable, for example, in fracturing treatments in that the interaction of the friction reducing polymer with formation fines may result in the coagulation of formation fines into flocs. The resulting flocs may be undesirable, among other things, because the flocs may facilitate the formation of a stable emulsion in the formation possibly undesirably impacting subsequent production from the well bore.